Problems associated with the use of fossil fuels, such as global warming, environmental degradation, rising energy costs, peak oil, and global conflicts, have created a need for a solar based economy. Cost competitive solar energy production will probably be required before this goal can be reached. Flat panel solar electric (PV cell) collectors are relatively expensive. Attempts to economize solar energy include concentrating parabolic reflectors that only work in direct sunlight. Even haze or smog reduce the direct sunlight collected. Significant costs are incurred for critical reflector shape, support structure, sun tracking capability, and transmission loss to less sunny regions. Flat panel PV cell collectors are simple to construct, can be stationary and hemi-spherically collect ambient radiant energy, however they operates less efficiently with diffuse only light.
Attempts to combine the best of flat panels, and parabolic concentrators include compound parabolic concentrators (CPC). CPCs use reflectors to concentrate (CR) and collect ambient light over a limited angle of acceptance (AOA) according to the ideal 2-D relationship, CR=1/sin(half AOA). CPC reflector's are usually truncated in height, with a reduced CR and collect some light outside the AOA. CPC variants sometimes use transparent refractors. These types of collectors are more generally called radiant energy traps. Designs include those by Eshelman, Knowles, Winston, Gill, Vasylyev, Isofoton S.A., and Sci Tech U.S.A., and European patents EP0070747 and DE 3233081. Refractors are used in designs by Kapany, Johnson, Winston, Lee, Chemey, Fereidooni, Chen and in Bowden's designs, from the University of New South Wales. The main problem with prior art is that they suffer from a relatively small AOA, or too low a diffuse light CR-AOA combination. The material and manufacturing costs are usually too high for the relative size of the aperture (A) to the refractor size, or reflector area, described as the length of the reflector curve (RL) or height (H), as the ratios; RL/A and WA respectively. 3-D concentrators, such as those in Steigerwald's patent #DE10059555 A1, Puall's patent application #20050081909, Lichy's patent application #20060072222, Bowden's thesis, Murtha's U.S. Pat. Nos. 6,021,007 and 6,619,282 also suffer from low CR for the AOA or unreasonably high optics costs, compared to the current invention.
Additional problems with solar power need to be addressed. Installed system payback periods are too long to be generally accepted. In seasonal climates, providing most of a buildings thermal and electrical needs would require an unreasonably large un-shaded solar collector area. PV cell efficiency drops in the hot sun. Even cooled cells waste about 80% of the radiant energy striking them. A hybrid collector combines electric and thermal functions. Numerous hybrid systems have been attempted, as in Mlausky and Winston's U.S. Pat. No. 4,045,246, Damsker's U.S. Pat. No. 4,395,582, Goldman's U.S. Pat. No. 4,427,838, the “CHAPS” project at Australian National University, CPC designs, by Brogren at Uppsala University in Sweden, Puall's patent application #20050081909, Johnson's U.S. Pat. No. 6,080,927 or Nicoletti's U.S. Pat. No. 7,173,179. These designs have small AOA for the CR, poor energy utilization, require sun tracking or are cost prohibitive relative to the current invention.